Color-stable vinyl chloride polymers



United States Patent 3 225 001 COLOR-STABLE VIN YL EIHLORIDE POLYMERSGeorge J. Darsa, Bronx, N.Y., assignor to National Lead Company, NewYork, N.Y., a corporation of New Jersey N0 Drawing. Filed Mar. 27, 1961,Ser. No. 98,301

8 Claims. (CI. 26045.75)

This invention relates to the stabilization of resinous compositionscontaining vinyl chloride polymers and copolymers. in particular thisinvention relates to an improved vinyl chloride resin compositionstabilized as to the deleterious effects of heat and light.

The problem of stabilizing vinyl chloride resins at elevatedtemperatures is one of long duration. Primarily, most of the stabilizerresearch has been directed toward providing adequate stabilizingmaterials which will protect the plastic, both in the formation stagesand finished com positions, against the deleterious effects of heat andlight. Utilization of higher processing temperatures has required theart to develop new materials and means to inhibit or delay thediscoloration and subsequent loss of properties of the vinyl chlorideresins. Although slight discoloration on heating may not detract to anyappreciable extent from the physical properties of the resin, thediscoloration limits the usefulness in many applications. While many ofthe current stabilizers have effected substantial improvements inproviding stabilized plastics, there is still much to be desired in theresults obtained.

For many current applications of vinyl resins, the resin is compoundedso as to produce a clear, transparent plastic product. In applicationswhere clear vinyl plastics are used, the stabilizer, in addition tofulfilling its primary function, must be of such a nature that it doesnot impair the clarity of the finished product. Some of the best of theconventional heat-stabilizers are unacceptable for use in clear vinylformulations because they impair clarity, leading to hazy or even opaqueproducts.

It is therefore an object of this invention to provide a novelstabilizer for vinyl chloride polymer and copolymer resins. Anotherobject is to provide an improved heatstabilizer for vinyl chloridecontaining resins. Still another object is to provide a stabilizer asaforesaid, which is capable of use in clear vinyl plastic formulationsand does not impair the clarity thereof. Other objects and advantageswill become apparent from the following more complete description andclaims.

Broadly, this invention contemplates an auxiliary stabilizer for vinylchloride polymer and copolymer resins comprising a hindered bisphenoland a trivalent-organophosphorus compound, said hindered bisphcnolcorresponding to the formula:

OH OH where R R R and R are alkyl groups having a maximum of 4 carbonatoms and said trivalent organo-phos' phorus compound corresponds to oneof the following formulae: (RO) P and (ROhPR', where R and R areradicals selected from the group consisting of aliphatic hydrocarbonradicals containing from 1 to 18 carbon 3,225,001 Patented Dec. 21, 1965atoms and aryl radicals containing from 6 to l 8 carbon atoms. Thisinvention further contemplates an improved plastic compositioncomprising a vinyl chloride resin, and

a stabilizer according to the present invention.

In a particularly desirable embodiment, this invention contemplates acombination of three stabilizing components, namely a multivalent metalsalt primary stabilizer and an auxiliary stabilizer consisting of ahindered bis phenol and a trivalent organo-phosphorus compound.

The multivalent metal salt primary stabilizers are well known to theart. Typical of those stabilizers used in vinyl chloride resincompositions are the multivalent metal phenolates and multivalent metalcarboxylates. The multivalent metals are selected from the groupconsisting of the alkaline earth metals, magnesium, cadmium, zinc, andaluminum. Examples of phenols that may be used in the form of metalphenolates we mention: methyl-, ethyl-, butyl-, amyl-, octyl-, nonyl-,dodecyl-, octadecyl-, and oleylphenol; di'butyl-, diamyl-, dinonylanddidodecylphenol. The carboxylates may be aromatic or aliphatic. Asexamples of aromatic carboxylates we mention benzoate, p-tertiarybutylbenzoate, benzoylbenzoate and as aliphatic carboxylatcs we maymention 2-ethylhcxoate, caprate, laurate, stearate, oleate andricinoleate. The multivalent metal salt stabilizers may be used singlyor preferably in combination. Such combinations may include mixture ofthe salts of barium and cadmium, barium and zinc; calcium and zinc; etc.

The hindered bisphenols useful in this invention are those representedby the formula:

where R R R and R are alkyl groups, each group containing a maximum of 4carbon atoms and where R; and R, are preferably tertiary alkyl groupsand where all positions ortho and para to the hydroxyl groups havesubstituted hydrocarbon radicals. Examples are 2,2'-methylenebis-4-rnethyl-6-tertiary butylphenol, 2,2'-methylene bis-4ethyI-6-=tertiary butylphenol, 2,2'-methylene bis-4- tertiarybutyl-tS-methylphenol, and 2,2'-mcthylene bis-4,6- tertiary butylphenol.

The trivalent organo-phosphorus compounds may be from the groupconsisting of phosphites and phosphonites represented by theirrespective formulae (RO) P and (RO),PR', where R and R representradicals selected from the group consisting of aliphatic hydrocarbonradicals containing from 1 to 18 carbon atoms and aryl radicalscontaining from 6 to 18 carbon atoms. Examples of such compounds arealkyl and aryl phosphites such as triphenyl-, tricresyl-, dioctylphenyl-, and tn'octylphosphite and dinonylphenyland dioctylbenzenephosphonites.

The manipulative procedure is the same in all cases, whether thecontemplated material is a phosphite or a phosphonite.

The color-preservative auxiliary stabilizer consisting of a hinderedbisphenol and a trivalent organo-phosphorus compound, as describedabove, may be combined in a single package along with themultivalent-metal salt primary stabilizer or may be contained in aseparate package. in addition, the hindered bisphcnol and tri- Methodsfor the preparation of the hindered bisphenol and trivalentorgano-phosphorus compounds are well known to the art and constitute nopart of the present invention. A wide range in the proportion ofmultivalent metal salt primary stabilizer to auxiliary stabilizer iseffective, and the desired proportions may be left to the discretion ofthe compounder. We have attained good results by incorporating fromabout 0.05 to about 10.0 parts of an auxiliary stabilizer andparticularly good results from about 0.1 to about 5.0 parts of anauxiliary stabilizer consisting of a hindered bisphenol and a trivalentorgano-phosphorus compound, per 1 part of multivalent metal salt primarystabilizer. In general, for 100 parts of a vinyl chloride resin, fromabout 0.6 toabout 10.0 parts of a primary plus auxiliary stabilizerisemployed.

The auxiliary stabilizer composition also may vary over a wide range,but in general for good results the hindered bisphenol should be presentfrom about 0.005 to about parts per 1 part of trivalentorgano-phosphorus compound. For 100 parts of a vinyl chloride polymer orcopolymer resin, we-have attained good results by incorporatingfromabout 0.001 to about 2.0 parts of hindered bisphenol and preferablyfrom about- 0.005 to 1.0 part; andfrom about 0.01 to about 10.0 parts oftrivalent organo-phosphorus compound and preferably from about 0.1 toabout 1.0 part as the auxiliary stabilizer.

While hindered bisphenols (Myers et al., US. Patent No. 2,820,744) andorganic phosphites (Leistner .et al., US. Patent 2,564,646) have beenproposed separately as stabilizers, we have found that theircombination,.alo'ng with a metal salt stabilizer, has given anunexpected and synergistic effect in color stabilization. To be useful,the hindered bisphenols and trivalent organo-phosphorus compounds mustbe used with a primary stabilizer, where they exert a synergistic efiectand increase the overall efiectiveness of the combination. This overallincrease in effectiveness can, in manycases, reduce the amount ofprimary stabilizer heretofore necessary for maximum stabilization,thereby reducing some of the inherent problems found with primarystabilizers, among which we may mention clarity and plating.

The following examples, given by way of illustration, embody a specificresin, one primary plasticizer, one secondary plasticizer, two primarystabilizer systems and one lubricant for purposes of uniformity andcomparability. Other homopolymers, copolymers, plasticizers,

stabilizers and lubricants may be substituted in specific examplesyielding approximately the same results.

EXAMPLE I e The following compositions were weighed, mixed, heated on atwo-roll mill at a temperature of 315 F. and milled for three minutesuntil substantially uniform. The compositions were then sheeted into-mil sheets. The data set forth in Table I demonstrates the combinedeffect of a trivalent organo-phosphorus compound and a hinderedbisphenol;

Table I Composi- Composi- Composi- Composi- Component tion 1, tion 2,tion 3, tion 4,

parts by parts by parts by parts by weight weight weight weightPolyvinylehloride resin 100 100 100 Diootylphthalate- 40 40 40 40Epoxidized soybean Oil 3 3 3 3 Stearic acid." 0.5 0.5 0.5 0.5 Bariumnonylphen late 0. 5v 0. 5 0. 5 0. 5 Cadmium p-tbutylbenzoate 0. 25 0. 250. 25 0. 25 2,2'-methy1ene bis!- ethyl-Memory butylphenol- 0. 0 U. D 0.7 0. 3

Triphenyl phosphite 0. 0 0. 7 0. 0 0. 4

The plastic compositions were exposed to a temperature of 400 F. withperiodic sampling to determine heat stability. Composition 1, after 5minutes exposure, showed a light tan discoloration and after 15 minuteshad a pronounced yellow discoloration. Composition EXAMPLE II Thefollowing compositions were prepared and tested in the same manner as inExample I. This example demonstrates the effectiveness of the claimedauxiliary stabilizer of this invention when used in conjunction with aprimary stabilizer. Table II denotes the compositions.

Table II Composition Composition Composition Composition CompositionComponent 5, parts by parts by 7, parts by 8, parts by 9, parts byweight weight weight weight weight IVC resin. 100 100 100 100 100 OF 4040 40 40 40 Epoxy plastlcizer. 3 3 3 3 3 Stearic acid 0. 5 0. 5 0. 5 0.5 0. 5 Barium nonylphenolate 1. 0 2. 0 0.0 0. 0 1. 0 Cadmium p-trbutylbenzoate. 0. 5 1. O 0.0 0.0 0. 5 2,2-methylene bisA-ethyl-G-te 0. 0 O. 00. 3 0. 6 O. 3

butylphenol Triphenyl pbosphite 0. 0 0. 0 O. 4 0. 8 0. 4

Degree of discoloration Heat. stability 400 F;

After 10 min. exposure 11:. yellow. yellow deep red. deep red almostcolore55. Alter 25 min. exposure yellow dp. yel1ow v. dp. red-.. v. dp.red-.. v. lt. yellow.

The above tabulated results show that composition 9, namely the instantinvention, is more effective than composition 6 which contains twice theamount of primary stabilizer without any auxiliary stabilizer. itfurther shows that the total amount of stabilizer may be reduced in theplastic composition and yield better heat stability results.Compositions 7 and 8 demonstrate that the auxiliary stabilizer when usedalone has almostno stabilizing eflect and must be used in conjunctionwith a primary stabilizer to be effective.

EXAMPLE III Compositions containing 100 parts of a polyvinylchlorideresin, 40 parts of DOP, 3 parts of epoxy plasticizer, 0.5 part ofstearic acid, 1.0 part of barium nonylphenolate, 0.5 part of cadmiump-tertiary butylbenzoate, 0.1 part of 2,2'-methylenebis-4-ethyl-6-tertiary butylphenol and 0.4 part of a trivalentorgano-phosphorus compound were tested for heat stability and clarity.The trivalent organophosphorus compounds evaluated were octyl diphenylphosphonite, nonyl diphenyl phosphonite, phenyl diphenyl phosphonite,triphenyl phosphite and triisooctyl phosphi'te. The compositioncontaining the different phosphorus compounds all showed a good degreeof heat stability and clarity.

EXAMPLE 1V Compositions containing 100 parts of a polyvinyl chlorideresin, 40 parts of DOP, 3 parts of epoxy plasticizer, 0.5 partof stearicacid, 1.0 part of barium nonylphenolate, 0.5 .part of cadmium p-tertiarybutylbenzoate, 0.4 part of triphenylphosphite. and 0.1 part of, any oneof the hindered misphenols mentioned above .give good heat v stabilityresults.

EXAMPLE V Compositions similar to composition 4 of Example I wereprepared except that the concentration of the hindered bisphenol wasvaried from 0.0 to 2.50 parts. The results showed good heat stabilityresulted when the hindered bisphenol was present from about 0.001 toabout 2.0 parts and exceptional stability when the amount of bisphenolwas from about 0.005 to about 1.0 part.

EXAMPLE v11 Compositions containing 100 parts of a polyvinylchlorideresin, parts of DOP, 3 parts oi epoxy plasticizer, 0.5 part stearicacid, 1.0 part barium nonylphenolate, 0.5 part cadmiump-t-butylbenzoate, and 0.3 part of 2,2- methylene bis-4-ethyl-6-tertiarybutylphenol were prepared. The trivalent organo-phosphorus compound,triphenyl phosphite, was varied from 0.0 to 10.0 parts. The resultsshowed a useful degree of stabilization when the phosphorus compound waspresent from about 0.01 part to about 10 parts; good stabilization whenthe phosphorus compound was present from about 0.1 to about 1.0 part;and partitcularly good stabilization from about 0.4 part to about 0.6part.

As demonstrated by the examples, the objects of this invention have beenachieved, the method being fully dis closed can readily be carried outby persons without special skill and requires a minimum of equipment.Particular features of the vinyl chloride resin composition are (1) itsexceptional degree of color stabilization at elevated temperatures, (2)its high degree of stabilization against the deleterious effects of heatand (3) its exceptional clarity.

By the term vinyl chloride resin we mean to include the various vinylresins compounds and combinations known to the art, including polyvinylchloride; vinyl resins produced by copolymerizing vinyl chloride withvinyl acetate or other vinyl esters; vinyl resins produced bycopolymerization with an acrylic compound such as ethyl and methylmethacrylate; vinylidene chloride, and vinylvinylidene chloridecopolymers.

The stabilizers of this invention can be incorporated in chlorinecontaining vinyl resins alone or in conjunction with plasticizers,pigments, dyes, fillers, etc. The effectiveness of this invention isindependent of the method or process employed in producing objects oritems, these operations including milling, calendering, molding,extrusion, etc.

While this invention has been described in terms of certain preferredembodiments and illustrated by means of specific examples, these areillustrative only, and the invention is not to be construed as limitedexcept as set forth in the following claims.

I claim:

1.' A plastic composition stable at temperatures above 375" F.comprising a polyvinyl chloride homopolymer resin and a stabilizerpresent in an amount from about 0.6 to about 10 parts of resin, saidstabilizer consisting essentially of (l) a primary stabilizer comprisinga combination of at least one member selected from the groupconsisting'ot barium phenolates and barium monocarboxylates and at leastone'member selected from the group consisting of cadmiummonocarboxylates and zinc monocarboxylates, and (2) an auxiliarystabilizer com-- prising a combination of a hindered bisphenolcorresponding to the formula OH OH RiOCIL-Olh Ra R;

where R R R and R are alkyl groups having a maximum of 4 carbon atomsand a trivalent organo-phos- 'phorus compound corresponding to one ofthe following formula, RO) P and (RO);PR', where R and R are radicalsselected from the group consisting of alkyl and aryl radicals containingfrom 6 to 15 carbon atoms, said hindered bisphenol being present fromabout 0.005 to about 10 parts per 1 part of said trivalentorgano-phosphorus compound, and where said auxiliary stabilizer ispresent from about 0.05 to about 10 parts per 1 part of said primarystabilizer.

2. A plastic composition according to claim 1, wherein said hinderedbisphenol is 2,2'-methylene bisA-rnethyl- 6-tertiary butylphenol. 1

3. A plastic composition according to claim 1, wherein said hinderedbisphenol is 2,2'methylene bis-4-ethyl- 6-tertiary butylphenol.

4. A plastic composition according to in said trivalentorgano-phosphorus compound is triphenyl phosphite.

5. A plastic composition according to claim 1, wherein said trivalentorgano-phosphorus compound is triisooctyl phosphite.

6. A lastic composition according to claim 1 wherein said trivalentorgano-phosphorus compound is octyl diphenyl phosphonite.

7. A plastic composition according to claim 1, wherein said trivalentorgano-phosphorus compound is nonyl diphenyl phosphonite.

claim 1,, where- 7 s 8. A plastic composition according to claim 1,wherein 2,935,491 5/1960 Mack 26045.95 said trivalent organo-phosphoruscompound is phenyl 2,985,617 5/1961 Salyer et a1. 26045.9 dlphenylphosphite. OTHER REFERENCES References Cited by the Examiner 5 Smith:British PlastiCs,

UNITED STATES PATENTS LEON I. BERCOVITZ, Primary Examiner. 2,716,0928/1955 Lcistncr ct a]. 260-4595 M STERMAN Examiner 2,820,774 1/1958Myers et a1. 26045.95

1. A PLASTIC COMPOSITION STABLE AT TEMPERATURES ABOVE 375*F. COMPRISINGA POLYVINYL CHLORIDE HOMOPOLYMER RESIN AND A STABILIZER PRESENT IN ANAMOUNT FROM ABOUT 0.6 TO ABOUT 10 PARTS OF RESIN, SAID STABLIZIERCONSISTING ESSENTIALLY OF (1) A PRIMARY STABILIZER CMPRISING ACOMBINATION OF AT LEAST ONE MEMBER SELECTED FROM THE GROUP CONSISTING OFBARIUM PHENOLATES AND BARIUM MONOCARBOXYLATES AND AT LEAST ONE MEMBERSELECTED FROM THE GROUP CONSISTING OF CADMIUM MONOCARBOXYLATES AND ZINCMONOCARBOXYLATES, AND (2) AN AUXILIARY STABILIZER COMPRISING ACOMBINATION OF A HINDERED BISPHENOL CORRESPONDING TO THE FORMULA